I. Field of the Invention
The invention relates to a thermometer probe or pyrometer for measuring the temperature in low-convection media.
II. Description of the Prior Art
Thermometer probes are known in which a temperature-dependent resistor, e.g. a thermistor, is integrally cast in a steel sleeve. The steel sleeve is connected to a holding device and the resistor connections are connected to an evaluation circuit. To permit accurate measurement of the temperature, the steel sleeve and, optionally, the holding device must assume the temperature of the medium whose temperature is to be measured. The thermal energy necessary for this ordinarily derived from the surrounding medium. This causes localized cooling. To compensate for this localized cooling, heat is taken from the more remote areas of the medium. This process occurs rapidly in media with strong convection properties allowing relatively rapid temperature measurement with the prior art thermometer probe. However, in low-convection or convection-free media, temperature compensation between the probe and the medium takes place very slowly, so that an accurate temperature measurement is very time-consuming. Where such long measuring periods are required, continuous heat transfer through the holding device and the connecting cables can result in erroneous readings. Similarly, the test current can generate enough heat due to resistance encountered in the circuit to introduce errors due to heating of the electrode.